It is often said that the $L_4$ and $L_5$ points are "60 degrees ahead and behind" a planet like Jupiter. Clearly this is true only in the case of circular orbits. In more elliptical orbits, I assume the rule of thumb would be that the $L_4$ and $L_5$ are at the points on the orbit that are equidistant from the planet and barycenter. Would that be a safe assumption?
In the more general case of elliptical orbits, there are no longer stationary points in the same sense: it becomes more of a Lagrangian “area”. The Lagrangian points constructed at each point in time, as in the circular case, form stationary elliptical orbits which are similar to the orbits of the massive bodies.
A more complete answer is given in this paper. It concludes that yes, L4 and L5 are at the points on the orbit that are equidistant from the planet and barycenter.